V8 EFI Engine surge

[msdani]

Hi everyone

I have a 90 Bronco 351 EFI and its had an idle surge 'issue' Its to the point now that I have to brake with my left foot so I can give it a bit of gas to stop it from stalling out! The stall happens intermittently and usually when RPM is 1500 and under. I can tell when it starts to happen while driving at freeway speeds/RPMs because power/tourge drops off. When pulling upto a traffic light and RPM starts to drop because throttle is released, the idle drops past the normal 600-700 mark and goes to almost 100 and then shoots up to 1500 for a second and drops back down to 0 and dies...!!!!!!!!!!! this almost got myself killed yesterday in heavy traffic. Ive talked with many mechanics and they tell me if the check engine light does not flash that the computer will not log a sensor error, so there is no way to tell by code if something is wrong. I have talked with several mechs and they have a wide variety of advice.

BTW, I have changed plugs, wires, cap and rotor! This Didn't work to fix surge.

#1 Change ERG Valve
#2 Change Ide/surge unit
#3 Change Coil
#4 Change out 02 Sensor
#5 Change Fuel pump
#6 Change fuel filter "Did this, didn't help"
#7 Change to Hi octane fuel "Did this, didn't help"
#8 Change plugs, cap and rotor "Did this, didn't help"
#9 Change Wire's "Did this, didn't help"
#10 check for vacuum leak "Did this, didn't help"

Anyone have any ideas on this?? I really don't want to take it to a dealership if I don't have to cause they seem to know less then I do about what causes a intermittent surge and stall.

Thanks,
Danielle

 

[Pancholin]

Msdani.
When you get to #5 be sure to check the fuel pickup tube inside the fuel tank. I have had two of them crack and the symptoms were similar to yours, but the main difference was when the tank was full it ran just fine. As the tank got lower the missing and dying got worse, and it is NOT fun to have a diesel die with air in the lines. It is even less fun when you are forty miles into the desert. I'll blame it on washboard roads. The pump attached to the gas pickup tube on the Trooper caused the same thing but it was cracked right at the top so it always ran bad but the crack wasn't too bad and it was harder to find. Wouldn't transparent fuel line be nice? I could have see the bubbles right off.
Pancholin